From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Darren Hart <dvhart@infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Darren Hart <darren@dvhart.com>, Ingo Molnar <mingo@kernel.org>,
Michael Kerrisk <mtk.manpages@googlemail.com>,
Davidlohr Bueso <dave@stgolabs.net>, Chris Mason <clm@fb.com>,
"Carlos O'Donell" <carlos@redhat.com>,
Torvald Riegel <triegel@redhat.com>,
Eric Dumazet <edumazet@google.com>
Subject: Re: [patch V2 3/7] futex: Add op for hash preallocation
Date: Thu, 19 May 2016 14:28:49 +0200 [thread overview]
Message-ID: <20160519122849.GD3192@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <alpine.DEB.2.11.1605071046130.3540@nanos>
On Sat, May 07, 2016 at 10:47:38AM +0200, Thomas Gleixner wrote:
> On Fri, 6 May 2016, Darren Hart wrote:
> > So this seems like it could be tricky for the user as system libraries, like
> > glibc, make use of futexes. Can we guarantee that "sys_futex" is not called by
> > the time main() is called?
>
> To the extent of my testing I never observed that the hash was automatically
> created when I called futex(PREALLOC) right away in main. But yes, that might
> need some thought.
I suspect that even if glibc uses futexes before main(), they will not
be contended, because, last time I checked, the C runtime environment is
very much single threaded unless explicitly made not so by the program.
In any case (re)hashing if the hash is empty is 'easy', if there's already state,
not so much.
next prev parent reply other threads:[~2016-05-19 12:28 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-05 20:44 [patch V2 0/7] futex: Add support for process private hashing Thomas Gleixner
2016-05-05 20:44 ` [patch V2 1/7] futex: Add some more function commentry Thomas Gleixner
2016-05-06 17:37 ` Darren Hart
2016-05-05 20:44 ` [patch V2 2/7] futex: Hash private futexes per process Thomas Gleixner
2016-05-06 18:09 ` Darren Hart
2016-05-06 21:56 ` Darren Hart
2016-05-07 8:45 ` Thomas Gleixner
2016-05-11 21:08 ` Darren Hart
2016-05-07 8:44 ` Thomas Gleixner
2016-05-11 21:07 ` Darren Hart
2016-05-27 16:36 ` Sebastian Andrzej Siewior
2016-05-19 12:21 ` Peter Zijlstra
2016-05-27 16:52 ` Sebastian Andrzej Siewior
2016-05-30 8:43 ` Peter Zijlstra
2016-05-19 12:24 ` Peter Zijlstra
2016-05-27 17:10 ` Sebastian Andrzej Siewior
2016-05-30 8:58 ` Peter Zijlstra
2016-05-30 11:08 ` Sebastian Andrzej Siewior
2016-05-30 12:06 ` Peter Zijlstra
2016-05-30 13:37 ` Sebastian Andrzej Siewior
2016-05-30 13:49 ` Peter Zijlstra
2016-05-30 13:59 ` Sebastian Andrzej Siewior
2016-05-30 14:02 ` Peter Zijlstra
2016-05-05 20:44 ` [patch V2 3/7] futex: Add op for hash preallocation Thomas Gleixner
2016-05-06 18:18 ` Darren Hart
2016-05-07 8:47 ` Thomas Gleixner
2016-05-07 11:40 ` Thomas Gleixner
2016-05-19 12:28 ` Peter Zijlstra [this message]
2016-05-19 19:36 ` Darren Hart
2016-05-19 12:24 ` Peter Zijlstra
2016-05-19 19:38 ` Darren Hart
2016-05-20 4:50 ` Peter Zijlstra
2016-05-19 12:25 ` Peter Zijlstra
2016-05-27 17:27 ` Sebastian Andrzej Siewior
2016-05-30 8:59 ` Peter Zijlstra
2016-05-05 20:44 ` [patch V2 4/7] futex: Add sysctl knobs for process private hash Thomas Gleixner
2016-05-06 18:22 ` Darren Hart
2016-05-27 17:33 ` Sebastian Andrzej Siewior
2016-05-05 20:44 ` [patch V2 5/7] perf/bench/futex-hash: Support NUMA Thomas Gleixner
2016-05-05 20:44 ` [patch V2 6/7] perf/bench/futex-hash: Support preallocate hash table Thomas Gleixner
2016-05-05 20:44 ` [patch V2 7/7] futex.2: Document hash preallocation opcode Thomas Gleixner
-- strict thread matches above, loose matches on Subject: below --
2016-05-05 19:03 [patch V2 0/7] Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Linus Torvalds <torvalds@linux-foundation.org>, Darren Hart <darren@dvhart.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, Michael Kerrisk <mtk.manpages@googlemail.com>, Davidlohr Bueso <dave@stgolabs.net>, Chris Mason <clm@fb.com>, Carlos O'Donell <carlos@redhat.com>, Torvald Riegel <triegel@redhat.com>, Eric Dumazet <edumazet@google.com> Thomas Gleixner
2016-05-05 19:03 ` [patch V2 3/7] futex: Add op for hash preallocation Thomas Gleixner
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